This invention relates generally to equipment used in testing electronic packages, such as integrated circuits, and more particularly to contact probes mounted in sockets for interfacing electronic packages with test equipment.
Typically, during testing electronic packages, such as integrated circuit (IC) packages, such packages are removably mounted in sockets which in turn are mounted on a circuit substrate, commonly referred to as a device-under-test (DUT) or load board. The sockets mount individual contact probes for electrically connecting each terminal of a device to be tested to an individual circuit path on the DUT board. The DUT board is in turn electrically connected to computerized test equipment. Over time the contact tips of the probe plungers which make connection with the electronic package tend to become contaminated with solder from solder of the terminals of the packages being tested. Conventionally, when the contact tips become contaminated the contact probes are replaced. The contaminated contract probes are either discarded or, in view of the fact that the remaining structure has a long life expectancy, are recycled by putting the contact tips in a suitable caustic cleaner or brushing off the contact tips. However, cleaning and brushing also removes gold plating material from the contact tips, pushes the solder around, is labor intensive and can result in contamination in the inner workings of the contact probe.
Objects of the present invention are to provide an improved socket and contact probes which overcome the prior art limitations noted above. Another object of the invention is the provision of a contact probe in which contact tips are more easily maintained in optimum operational condition than in the prior art. Still other objects of the invention are the provision of a socket and contact probes used therewith which are less expensive to maintain in optimum operational condition.
Briefly, in accordance with a preferred embodiment of the invention, a socket used in connection with testing electronic packages, such as integrated circuits, has a base member formed with a plurality of spaced apart bores which extend vertically therethrough and are arranged in a pattern corresponding to the terminal array of the electronic package. An electrical contact probe assembly is received in each bore, the assembly comprising a barrel formed of electrically conductive material and formed with a first closed end having a lower electrical contact tip which extends beyond the bottom surface of the base member for electrical engagement with a contact pad on a circuit board on which the socket is mounted. Another upper contact tip in the form of an upper plunger having an elongated portion at an end thereof is slidably and removably received in an open second end of the barrel and has a second end formed with a selected contact configuration. The upper plunger is slidable inwardly against the bias of a coil spring and is slidably removable from the barrel. In selected embodiments the removable upper plunger is formed with an outwardly radially extending annular shelf between the elongated portion of the upper plunger and the selected contact configuration. The socket preferably has a retainer member mounted on the base member with the retainer member formed with a plurality of vertically extending bores aligned with the vertically extending bores in the base member and provided with a stop surface in each bore thereof limiting outward movement of the plunger from the second end of the barrels as by engaging respective annular shelves. Removal of the retainer member enables one to readily remove any or all of the upper plungers for replacement and/or cleaning.
According to several embodiments, a member is disposed in each barrel between the respective upper contact tip and the coil spring. Preferably, the interengaging surfaces of the insulative member and the plunger are formed so that a lateral force is imparted to the contact tip biasing the elongated portion into good electrical contact with the barrel.
In several preferred embodiments the coil spring is received within the barrel between contact tips at opposite ends of the barrel. In one preferred embodiment the coil spring is disposed externally around the outside surface of the barrel with one end of the spring held in place by deforming the first end of the barrel by pressing an oversize insert portion of a contact tip which causes the barrel to bulge outwardly. The coil spring is chosen having an inside diameter less than the diameter of the bulged portion so that once the spring is pressed over the bulged portion it is held securely in place.
Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and methods particularly pointed out in the appended claims.